JPS5857641B2 - deaerator - Google Patents

Description

[Detailed description of the invention] The present invention relates to a deaerator that degass dissolved gas in a liquid.

Conventional deaerators, like deaerators in thermal power plants, heat condensate, raise the temperature to the saturation temperature of the deaerator's internal pressure, and then drop several trays in a cascade. Due to this, there are many types of degassing.

Figure 1 shows the cross section of the deaeration chamber of a conventional deaerator.
A heating steam pump 2 is provided in the lower part, a water injection valve 3 that spouts out water and a vent outlet 4 are provided in the upper part of the deaeration chamber 1, and a water supply injector 4 is provided in the lower end of the deaeration chamber 1. An outlet pipe 5 is provided.

A distribution tray 6 is provided below the water injection valve 3, and a deaeration tray 7 is formed below the distribution tray 6.

Heating steam thus flows from the heating steam port 2 into the deaeration chamber 1, and feed water flows from the feed water injection valve 3 suitably arranged in the upper part of the deaeration chamber 1.

The feed water injection valve 3 has a structure suitable for causing the ejected feed water to flow out in a thin film radial shape at the outlet, and the thin film of water and the heated steam rising from the bottom directly contact each other to exchange heat, and the water to be fed flows out. is raised to a temperature close to the saturation temperature of the internal pressure of the deaerator.

The feed water whose temperature has increased falls onto a distribution tray 6 provided to allow the feed water to fall uniformly onto a deaeration tray 7.

The supplied water is uniformly spread within the degassing chamber 1 by the distribution tray 6, and further falls onto the degassing tray 7 at the bottom.

The deaeration tray 7 stores the feed water close to the saturation temperature that has fallen from the upper part, and the overflowed feed water falls to the lower tray.

At that time, it is heated to the saturation temperature by contacting the heated steam rising from the bottom.

Incidentally, the amount of dissolved oxygen contained in the water supply follows Henry's law and Dalton's law, but dissolved oxygen is released from the liquid into the gas due to diffusion at the gas-liquid interface.

Therefore, in order to minimize the amount of dissolved oxygen, it is necessary to raise the liquid to the saturation temperature of the operating pressure of the container and to increase the surface area of the water. are installed to increase the diffusion effect.

In this type of deaerator, steam and feed water flow in opposite directions at the degassing tray 7, and when the rising speed of the steam increases, the rising steam flow causes the falling feed water flow to stop and stagnate.

This induces so-called flooding.

Therefore, there is a natural limit to miniaturization, and as the load decreases, the effect of steam flow rate almost disappears, so there is less freedom in terms of performance.

The present invention has been made in view of the above points, and an object of the present invention is to prevent the induction of flooding and provide a small and high-performance deaerator.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 shows an outline of the structure of a deaerator according to an embodiment of the present invention.

In FIG. 2, reference numeral 8 denotes a main body shell forming a rigid cylindrical pressure vessel, and inside the main body shell 8, there are slits 9 provided radially with respect to its central axis, or a large number of circular holes. It is divided into two by an open partition wall 10.

Further, in the center of the partition wall 10, there is a protrusion 11 that is reduced upwardly, a steam extraction pipe 12 is communicated from above the protrusion 11, and a steam extraction seat 13 is provided outside the main body shell 8. It is being

Further, the degassing heating steam input account 14 is attached to the body of the upper degassing chamber 15 of the two rooms divided by the partition wall 10, and communicates with the steam distribution box 16 disposed in the center. There is.

A ring tray 18 protrudes inward from the inner surface of the main body shell 8 above the disk tray 17 disposed in the steam distribution box 16.
is provided, and the upper part of the partition wall 10 in the lower part of the degassing chamber 15 is
The first hot well 19 is formed, and the lower part of the partition wall 10 is
A flash chamber 20 and a secondary hot well 21 below it
is formed.

Next, FIG. 3 shows a cross-sectional view of the steam distribution box 16 taken along a plane including the central axis of the degassing/heating steam inlet port 14 and the central axis of the main body shell 8.

In FIG. 3, the steam distribution box 16 has a large number of circular holes 22a.
, 22b are bored into the cylinders 23a and 23b, and the cylinder 23
a A lower lid 24a and a cylinder 23b an upper lid 24b, and a disk tray 17 that connects the middle of the cylinders 23a and 23b.
The diameters of the cylinders 23a, 23b and the diameter and number of the circular holes 22a, 22b are determined so as to appropriately distribute the steam.

The explanation will now return to FIG. 2 again.

The supplied water flows out from the water injection valve 3 disposed at the top of the degassing chamber 15 and flows out into the degassing chamber 15 radially from the center.

The feed water that has flowed into the degassing chamber 15 falls onto the ring tray 18 while being heated by the heated steam rising from the lower part, and then from the ring tray 18 to the steam distribution box 1 at the lower part.
6, and from the disk tray 17 it falls into the primary hot well 19 at the bottom.

In this way, the supplied water falls through the ring tray 18 and the disc tray 17 before reaching the primary hot well 19 from the water supply injection valve 3, and is heated by the degassing heating steam, and is heated inside the degassing chamber 15. The temperature rises to near the pressure saturation temperature.

Based on past empirical facts and experiments, the temperature rise from the water supply injection valve 3 to the ring tray 18 is caused by the difference between the water supply inlet temperature and the saturation temperature of the internal pressure of the degassing chamber 15. Approximately 85% to 90% of △θ, ring tray 18
and the first hot well 1 via the disk tray 17.
It has been found that a temperature increase close to 100% can be obtained by the time the temperature reaches 9.

Therefore, according to Henry's law and Dalton's law,
Dissolved oxygen in the water supply is almost completely degassed in the degassing chamber 15.

The degassed dissolved oxygen accumulates in the degassing chamber 15, and in order to prevent the partial pressure of oxygen in the degassing chamber 15 from increasing, the water injection valve 3 at the upper part of the degassing chamber 15 and two concentrically connected It has a double pipe structure, and passes through the outer pipe and is discharged from the vent outlet 4 to the outside of the system together with accompanying steam.

Connect the pipe leading to the vent outlet 4 to the outside of the water injection valve 3.
The reason for the double pipe structure is that the temperature of the feed water flowing inside the feed water injection valve 3 is always lower than the temperature of the vent steam, so the steam that comes into contact with the outer wall of the feed water injection valve 3 condenses and falls into the degassing chamber 15. This is because reducing the amount of vent steam released outside the system helps improve the heat rate of the plant.

The primary hot well 19 is formed on the partition wall 10,
The heated feed water flows into the lower flash chamber 20 through the slit 9 formed in the lower part of the partition wall 10.

Steam extraction pipe 12 arranged in the upper part of the flash chamber 20
By constantly extracting steam from the system to a system not shown,
The pressure within the flash chamber 20 will be maintained at a lower pressure than the pressure within the degassing chamber 15.

Since the feed water flowing in from the slit 9 is close to the saturation temperature of the pressure in the degassing chamber 15, the feed water flowing into the flash chamber 20 whose pressure is lower than the pressure in the degassing chamber 15 becomes thermodynamically unstable.

In other words, in the flash chamber 20, the gas phase and liquid phase are in a stable state at the saturation temperature corresponding to the pressure, but the saturation temperature with respect to the pressure in the flash chamber 20 is
Because it is lower than the saturation temperature for the pressure inside the deaeration chamber 15,
The feed water entering the flash chamber 20 cannot maintain a liquid phase.

Therefore, as is commonly known, the flash chamber 20
At the same time, an evaporation phenomenon occurs.

The amount of evaporation in this case is, as known from general thermodynamics,
The change of state from liquid phase to gaseous phase during evaporation is determined by the consumption of energy in the form of latent heat.

In other words, the amount of steam GSF (kg/h) flowing out from the flash chamber 20 through the steam extraction pipe 12 to the outside of the system is calculated as follows.

Tadakoshi GWD is the flow rate (kg/h) of water flowing into the flash chamber 20, and iWD is the first hot well 19.
Enthalpy of water supply (K c a 1 /ky)
, iWF is the enthalpy of saturated water with respect to the internal pressure of the flash chamber 20 (Kcal/kg), and iSF is the enthalpy of saturated water with respect to the internal pressure of the flash chamber 20.
Enthalpy of dry saturated steam (K c
a l Ay>.

The feed water flowing into the flash chamber 20 has 1. most of the dissolved oxygen removed in the degassing chamber 15. Dissolved oxygen concentration is very low.

The water further flows into the flash chamber 20 and continues to undergo the evaporation process from inside the liquid by boiling under reduced pressure, so the feed water accumulated in the secondary hot well 21 almost completely reaches the saturation temperature with respect to the pressure of the flash chamber 20. Therefore, complete deaeration is achieved.

As explained above, according to the present invention, the main body body forming the cylindrical pressure volume 4 is divided into two by a partition wall having a slit,
The upper part is a deaeration chamber, the lower part is a flash chamber, a ring tray and a disk tray are installed in the deaeration chamber, a primary hot well is formed on the upper part of the partition wall, and the main body of the deaeration chamber is heated for deaeration. A steam inlet port is installed and communicated with a steam distribution box installed in the center of the deaeration chamber, and water is injected in a radial direction from a water injection valve installed at the top of the deaeration chamber to the ring tray and disc tray. The heated steam from the steam distribution box (which is heated up) prevents the induction of flanding and is almost completely degassed in the degassing chamber. Furthermore, by boiling under reduced pressure in the flash chamber at the bottom of the partition wall, complete deaeration can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a deaeration chamber of a conventional deaerator, FIG. 2 is a schematic cross-sectional view of a deaerator according to an embodiment of the present invention, and FIG.
The figure is a cross-sectional perspective view of the main part of the same figure as above. 2... Heating steam inlet, 3... Water supply injection valve, 4... Vent outlet, 6... Distribution tray, 7... Deaeration tray, 8... Main body shell, 10... Partition wall, 12... Steam extraction pipe, 14... Deaeration heating steam inlet port, 15.・
... Deaeration chamber, 16 ... Steam distribution box, 17.
... Disc tray, 18 ... Ring tray, 19 ... First hot well, 20 ...
...Flash room.

Claims (1)

[Claims] 1 The main body, which is a cylindrical pressure vessel, is divided into two parts by a partition wall having slits, the upper part of which is a deaeration chamber, and the lower part of which is a flash chamber. A ring tray and a disk tray are provided in the deaeration chamber, and a first Next form a hot well,
A degassing heating steam inlet is provided in the main body of the degassing chamber, which communicates with the steam distribution box installed in the center of the degassing chamber. On the outside of the water supply injection valve that injects water to A deaerator characterized by: